Dynamic-threshold Admission Control with Negotiation in Multimedia Servers

Abstract

A novel threshold-based admission control algorithm with negotiation for two priority classes of requests is proposed in this study. The server capacity is divided into three partitions based on the threshold values：one for each class of requests and one common pool shared by two classed of requests. Given the characteristics of the system workload, the proposed algorithm finds the best partitions, optimizing the system performance based on the objective function of the total reward minus the total penalty. The negotiation mechanism will reduce the QoS requirements of several low-priority clients, by cutting out a small fraction of the assigned server capacity, to accept a new high-priority client and to achieve a higher net earning value. Stochastic Petri-Net model is used to find the optimal threshold values and two approzimation approaches are developed to find sub-optimal settings. The experiment results show that the proposed algorithm performs better than one without negotiation mechanism, and that the sub-optimal solutions found by the proposed approximation approaches are very close to optimal ones. The approximation approaches enable the algorithm to dynamically adjust the threshold values, based on the characteristics of the system workload, to achieve higher system performance.